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  <div class="SECT1">
    <h1 class="SECT1"><a name="CODING" id="CODING">4. Coding
    Guidelines</a></h1>

    <div class="SECT2">
      <h2 class="SECT2"><a name="S1" id="S1">4.1. Introduction</a></h2>

      <p>This set of standards is designed to make our lives easier. It is
      developed with the simple goal of helping us keep the "new and improved
      <span class="APPLICATION">Privoxy</span>" consistent and reliable. Thus
      making maintenance easier and increasing chances of success of the
      project.</p>

      <p>And that of course comes back to us as individuals. If we can
      increase our development and product efficiencies then we can solve
      more of the request for changes/improvements and in general feel good
      about ourselves. ;-&gt;</p>
    </div>

    <div class="SECT2">
      <h2 class="SECT2"><a name="S2" id="S2">4.2. Using Comments</a></h2>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S3" id="S3">4.2.1. Comment, Comment,
        Comment</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>Comment as much as possible without commenting the obvious. For
        example do not comment "variable_a is equal to variable_b". Instead
        explain why variable_a should be equal to the variable_b. Just
        because a person can read code does not mean they will understand why
        or what is being done. A reader may spend a lot more time figuring
        out what is going on when a simple comment or explanation would have
        prevented the extra research. Please help your brother IJB'ers
        out!</p>

        <p>The comments will also help justify the intent of the code. If the
        comment describes something different than what the code is doing
        then maybe a programming error is occurring.</p>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
/* if page size greater than 1k ... */
if ( page_length() &gt; 1024 )
{
    ... "block" the page up ...
}

/* if page size is small, send it in blocks */
if ( page_length() &gt; 1024 )
{
    ... "block" the page up ...
}

This demonstrates 2 cases of "what not to do".  The first is a
"syntax comment".  The second is a comment that does not fit what
is actually being done.
</pre>
            </td>
          </tr>
        </table>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S4" id="S4">4.2.2. Use blocks for
        comments</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>Comments can help or they can clutter. They help when they are
        differentiated from the code they describe. One line comments do not
        offer effective separation between the comment and the code. Block
        identifiers do, by surrounding the code with a clear, definable
        pattern.</p>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
/*********************************************************************
 * This will stand out clearly in your code!
 *********************************************************************/
if ( this_variable == that_variable )
{
   do_something_very_important();
}


/* unfortunately, this may not */
if ( this_variable == that_variable )
{
   do_something_very_important();
}


if ( this_variable == that_variable ) /* this may not either */
{
   do_something_very_important();
}
</pre>
            </td>
          </tr>
        </table>

        <p><span class="emphasis EMPHASIS c2">Exception:</span></p>

        <p>If you are trying to add a small logic comment and do not wish to
        "disrupt" the flow of the code, feel free to use a 1 line comment
        which is NOT on the same line as the code.</p>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S5" id="S5">4.2.3. Keep Comments on their
        own line</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>It goes back to the question of readability. If the comment is on
        the same line as the code it will be harder to read than the comment
        that is on its own line.</p>

        <p>There are three exceptions to this rule, which should be violated
        freely and often: during the definition of variables, at the end of
        closing braces, when used to comment parameters.</p>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
/*********************************************************************
 * This will stand out clearly in your code,
 * But the second example won't.
 *********************************************************************/
if ( this_variable == this_variable )
{
   do_something_very_important();
}

if ( this_variable == this_variable ) /*can you see me?*/
{
   do_something_very_important(); /*not easily*/
}


/*********************************************************************
 * But, the encouraged exceptions:
 *********************************************************************/
int urls_read     = 0;     /* # of urls read + rejected */
int urls_rejected = 0;     /* # of urls rejected */

if ( 1 == X )
{
   do_something_very_important();
}


short do_something_very_important(
   short firstparam,   /* represents something */
   short nextparam     /* represents something else */ )
{
   ...code here...

}   /* -END- do_something_very_important */
</pre>
            </td>
          </tr>
        </table>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S6" id="S6">4.2.4. Comment each logical
        step</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>Logical steps should be commented to help others follow the intent
        of the written code and comments will make the code more
        readable.</p>

        <p>If you have 25 lines of code without a comment, you should
        probably go back into it to see where you forgot to put one.</p>

        <p>Most "for", "while", "do", etc... loops _probably_ need a comment.
        After all, these are usually major logic containers.</p>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S7" id="S7">4.2.5. Comment All Functions
        Thoroughly</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>A reader of the code should be able to look at the comments just
        prior to the beginning of a function and discern the reason for its
        existence and the consequences of using it. The reader should not
        have to read through the code to determine if a given function is
        safe for a desired use. The proper information thoroughly presented
        at the introduction of a function not only saves time for subsequent
        maintenance or debugging, it more importantly aids in code reuse by
        allowing a user to determine the safety and applicability of any
        function for the problem at hand. As a result of such benefits, all
        functions should contain the information presented in the addendum
        section of this document.</p>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S8" id="S8">4.2.6. Comment at the end of
        braces if the content is more than one screen length</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>Each closing brace should be followed on the same line by a
        comment that describes the origination of the brace if the original
        brace is off of the screen, or otherwise far away from the closing
        brace. This will simplify the debugging, maintenance, and readability
        of the code.</p>

        <p>As a suggestion , use the following flags to make the comment and
        its brace more readable:</p>

        <p>use following a closing brace: } /* -END- if() or while () or
        etc... */</p>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
if ( 1 == X )
{
   do_something_very_important();
   ...some long list of commands...
} /* -END- if x is 1 */

or:

if ( 1 == X )
{
   do_something_very_important();
   ...some long list of commands...
} /* -END- if ( 1 == X ) */
</pre>
            </td>
          </tr>
        </table>
      </div>
    </div>

    <div class="SECT2">
      <h2 class="SECT2"><a name="S9" id="S9">4.3. Naming Conventions</a></h2>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S10" id="S10">4.3.1. Variable
        Names</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>Use all lowercase, and separate words via an underscore ('_'). Do
        not start an identifier with an underscore. (ANSI C reserves these
        for use by the compiler and system headers.) Do not use identifiers
        which are reserved in ANSI C++. (E.g. template, class, true, false,
        ...). This is in case we ever decide to port Privoxy to C++.</p>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
int ms_iis5_hack = 0;
</pre>
            </td>
          </tr>
        </table>

        <p><span class="emphasis EMPHASIS c2">Instead of:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
int msiis5hack = 0; int msIis5Hack = 0;
</pre>
            </td>
          </tr>
        </table>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S11" id="S11">4.3.2. Function
        Names</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>Use all lowercase, and separate words via an underscore ('_'). Do
        not start an identifier with an underscore. (ANSI C reserves these
        for use by the compiler and system headers.) Do not use identifiers
        which are reserved in ANSI C++. (E.g. template, class, true, false,
        ...). This is in case we ever decide to port Privoxy to C++.</p>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
int load_some_file( struct client_state *csp )
</pre>
            </td>
          </tr>
        </table>

        <p><span class="emphasis EMPHASIS c2">Instead of:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
int loadsomefile( struct client_state *csp )
int loadSomeFile( struct client_state *csp )
</pre>
            </td>
          </tr>
        </table>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S12" id="S12">4.3.3. Header file
        prototypes</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>Use a descriptive parameter name in the function prototype in
        header files. Use the same parameter name in the header file that you
        use in the c file.</p>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
(.h) extern int load_aclfile( struct client_state *csp );
(.c) int load_aclfile( struct client_state *csp )
</pre>
            </td>
          </tr>
        </table>

        <p><span class="emphasis EMPHASIS c2">Instead of:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
(.h) extern int load_aclfile( struct client_state * ); or
(.h) extern int load_aclfile();
(.c) int load_aclfile( struct client_state *csp )
</pre>
            </td>
          </tr>
        </table>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S13" id="S13">4.3.4. Enumerations, and
        #defines</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>Use all capital letters, with underscores between words. Do not
        start an identifier with an underscore. (ANSI C reserves these for
        use by the compiler and system headers.)</p>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
(enumeration) : enum Boolean { FALSE, TRUE };
(#define) : #define DEFAULT_SIZE 100;
</pre>
            </td>
          </tr>
        </table>

        <p><span class="emphasis EMPHASIS c2">Note:</span> We have a standard
        naming scheme for #defines that toggle a feature in the preprocessor:
        FEATURE_&gt;, where &gt; is a short (preferably 1 or 2 word)
        description.</p>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
#define FEATURE_FORCE 1

#ifdef FEATURE_FORCE
#define FORCE_PREFIX blah
#endif /* def FEATURE_FORCE */
</pre>
            </td>
          </tr>
        </table>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S14" id="S14">4.3.5. Constants</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>Spell common words out entirely (do not remove vowels).</p>

        <p>Use only widely-known domain acronyms and abbreviations.
        Capitalize all letters of an acronym.</p>

        <p>Use underscore (_) to separate adjacent acronyms and
        abbreviations. Never terminate a name with an underscore.</p>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
#define USE_IMAGE_LIST 1
</pre>
            </td>
          </tr>
        </table>

        <p><span class="emphasis EMPHASIS c2">Instead of:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
#define USE_IMG_LST 1 or
#define _USE_IMAGE_LIST 1 or
#define USE_IMAGE_LIST_ 1 or
#define use_image_list 1 or
#define UseImageList 1
</pre>
            </td>
          </tr>
        </table>
      </div>
    </div>

    <div class="SECT2">
      <h2 class="SECT2"><a name="S15" id="S15">4.4. Using Space</a></h2>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S16" id="S16">4.4.1. Put braces on a line
        by themselves.</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>The brace needs to be on a line all by itself, not at the end of
        the statement. Curly braces should line up with the construct that
        they're associated with. This practice makes it easier to identify
        the opening and closing braces for a block.</p>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
if ( this == that )
{
   ...
}
</pre>
            </td>
          </tr>
        </table>

        <p><span class="emphasis EMPHASIS c2">Instead of:</span></p>

        <p>if ( this == that ) { ... }</p>

        <p>or</p>

        <p>if ( this == that ) { ... }</p>

        <p><span class="emphasis EMPHASIS c2">Note:</span> In the special
        case that the if-statement is inside a loop, and it is trivial, i.e.
        it tests for a condition that is obvious from the purpose of the
        block, one-liners as above may optically preserve the loop structure
        and make it easier to read.</p>

        <p><span class="emphasis EMPHASIS c2">Status:</span>
        developer-discretion.</p>

        <p><span class="emphasis EMPHASIS c2">Example exception:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
while ( more lines are read )
{
   /* Please document what is/is not a comment line here */
   if ( it's a comment ) continue;

   do_something( line );
}
</pre>
            </td>
          </tr>
        </table>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S17" id="S17">4.4.2. ALL control
        statements should have a block</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>Using braces to make a block will make your code more readable and
        less prone to error. All control statements should have a block
        defined.</p>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
if ( this == that )
{
   do_something();
   do_something_else();
}
</pre>
            </td>
          </tr>
        </table>

        <p><span class="emphasis EMPHASIS c2">Instead of:</span></p>

        <p>if ( this == that ) do_something(); do_something_else();</p>

        <p>or</p>

        <p>if ( this == that ) do_something();</p>

        <p><span class="emphasis EMPHASIS c2">Note:</span> The first example
        in "Instead of" will execute in a manner other than that which the
        developer desired (per indentation). Using code braces would have
        prevented this "feature". The "explanation" and "exception" from the
        point above also applies.</p>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S18" id="S18">4.4.3. Do not
        belabor/blow-up boolean expressions</a></h3>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
structure-&gt;flag = ( condition );
</pre>
            </td>
          </tr>
        </table>

        <p><span class="emphasis EMPHASIS c2">Instead of:</span></p>

        <p>if ( condition ) { structure-&gt;flag = 1; } else {
        structure-&gt;flag = 0; }</p>

        <p><span class="emphasis EMPHASIS c2">Note:</span> The former is
        readable and concise. The later is wordy and inefficient. Please
        assume that any developer new to the project has at least a "good"
        knowledge of C/C++. (Hope I do not offend by that last comment ...
        8-)</p>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S19" id="S19">4.4.4. Use white space
        freely because it is free</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>Make it readable. The notable exception to using white space
        freely is listed in the next guideline.</p>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
int first_value   = 0;
int some_value    = 0;
int another_value = 0;
int this_variable = 0;

if ( this_variable == this_variable )

first_value = old_value + ( ( some_value - another_value ) - whatever )
</pre>
            </td>
          </tr>
        </table>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S20" id="S20">4.4.5. Don't use white space
        around structure operators</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>- structure pointer operator ( "-&gt;" ) - member operator ( "." )
        - functions and parentheses</p>

        <p>It is a general coding practice to put pointers, references, and
        function parentheses next to names. With spaces, the connection
        between the object and variable/function name is not as clear.</p>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
a_struct-&gt;a_member;
a_struct.a_member;
function_name();
</pre>
            </td>
          </tr>
        </table>

        <p><span class="emphasis EMPHASIS c2">Instead of:</span> a_struct
        -&gt; a_member; a_struct . a_member; function_name ();</p>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S21" id="S21">4.4.6. Make the last brace
        of a function stand out</a></h3>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
int function1( ... )
{
   ...code...
   return( ret_code );

}   /* -END- function1 */


int function2( ... )
{
}   /* -END- function2 */
</pre>
            </td>
          </tr>
        </table>

        <p><span class="emphasis EMPHASIS c2">Instead of:</span></p>

        <p>int function1( ... ) { ...code... return( ret_code ); } int
        function2( ... ) { }</p>

        <p><span class="emphasis EMPHASIS c2">Note:</span> Use 1 blank line
        before the closing brace and 2 lines afterward. This makes the end of
        function standout to the most casual viewer. Although function
        comments help separate functions, this is still a good coding
        practice. In fact, I follow these rules when using blocks in "for",
        "while", "do" loops, and long if {} statements too. After all
        whitespace is free!</p>

        <p><span class="emphasis EMPHASIS c2">Status:</span>
        developer-discretion on the number of blank lines. Enforced is the
        end of function comments.</p>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S22" id="S22">4.4.7. Use 3 character
        indentions</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>If some use 8 character TABs and some use 3 character TABs, the
        code can look *very* ragged. So use 3 character indentions only. If
        you like to use TABs, pass your code through a filter such as "expand
        -t3" before checking in your code.</p>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
static const char * const url_code_map[256] =
{
   NULL, ...
};


int function1( ... )
{
   if ( 1 )
   {
      return( ALWAYS_TRUE );
   }
   else
   {
      return( HOW_DID_YOU_GET_HERE );
   }

   return( NEVER_GETS_HERE );

}
</pre>
            </td>
          </tr>
        </table>
      </div>
    </div>

    <div class="SECT2">
      <h2 class="SECT2"><a name="S23" id="S23">4.5. Initializing</a></h2>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S24" id="S24">4.5.1. Initialize all
        variables</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>Do not assume that the variables declared will not be used until
        after they have been assigned a value somewhere else in the code.
        Remove the chance of accidentally using an unassigned variable.</p>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
short a_short = 0;
float a_float  = 0;
struct *ptr = NULL;
</pre>
            </td>
          </tr>
        </table>

        <p><span class="emphasis EMPHASIS c2">Note:</span> It is much easier
        to debug a SIGSEGV if the message says you are trying to access
        memory address 00000000 and not 129FA012; or array_ptr[20] causes a
        SIGSEV vs. array_ptr[0].</p>

        <p><span class="emphasis EMPHASIS c2">Status:</span>
        developer-discretion if and only if the variable is assigned a value
        "shortly after" declaration.</p>
      </div>
    </div>

    <div class="SECT2">
      <h2 class="SECT2"><a name="S25" id="S25">4.6. Functions</a></h2>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S26" id="S26">4.6.1. Name functions that
        return a boolean as a question.</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>Value should be phrased as a question that would logically be
        answered as a true or false statement</p>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
should_we_block_this();
contains_an_image();
is_web_page_blank();
</pre>
            </td>
          </tr>
        </table>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S27" id="S27">4.6.2. Always specify a
        return type for a function.</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>The default return for a function is an int. To avoid ambiguity,
        create a return for a function when the return has a purpose, and
        create a void return type if the function does not need to return
        anything.</p>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S28" id="S28">4.6.3. Minimize function
        calls when iterating by using variables</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>It is easy to write the following code, and a clear argument can
        be made that the code is easy to understand:</p>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
for ( size_t cnt = 0; cnt &lt; block_list_length(); cnt++ )
{
   ....
}
</pre>
            </td>
          </tr>
        </table>

        <p><span class="emphasis EMPHASIS c2">Note:</span> Unfortunately,
        this makes a function call for each and every iteration. This
        increases the overhead in the program, because the compiler has to
        look up the function each time, call it, and return a value.
        Depending on what occurs in the block_list_length() call, it might
        even be creating and destroying structures with each iteration, even
        though in each case it is comparing "cnt" to the same value, over and
        over. Remember too - even a call to block_list_length() is a function
        call, with the same overhead.</p>

        <p>Instead of using a function call during the iterations, assign the
        value to a variable, and evaluate using the variable.</p>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
size_t len = block_list_length();

for ( size_t cnt = 0; cnt &lt; len; cnt++ )
{
   ....
}
</pre>
            </td>
          </tr>
        </table>

        <p><span class="emphasis EMPHASIS c2">Exceptions:</span> if the value
        of block_list_length() *may* change or could *potentially* change,
        then you must code the function call in the for/while loop.</p>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S29" id="S29">4.6.4. Pass and Return by
        Const Reference</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>This allows a developer to define a const pointer and call your
        function. If your function does not have the const keyword, we may
        not be able to use your function. Consider strcmp, if it were defined
        as: extern int strcmp( char *s1, char *s2 );</p>

        <p>I could then not use it to compare argv's in main: int main( int
        argc, const char *argv[] ) { strcmp( argv[0], "privoxy" ); }</p>

        <p>Both these pointers are *const*! If the c runtime library
        maintainers do it, we should too.</p>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S30" id="S30">4.6.5. Pass and Return by
        Value</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>Most structures cannot fit onto a normal stack entry (i.e. they
        are not 4 bytes or less). Aka, a function declaration like: int
        load_aclfile( struct client_state csp )</p>

        <p>would not work. So, to be consistent, we should declare all
        prototypes with "pass by value": int load_aclfile( struct
        client_state *csp )</p>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S31" id="S31">4.6.6. Names of include
        files</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>Your include statements should contain the file name without a
        path. The path should be listed in the Makefile, using -I as
        processor directive to search the indicated paths. An exception to
        this would be for some proprietary software that utilizes a partial
        path to distinguish their header files from system or other header
        files.</p>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
#include &lt;iostream.h&gt;     /* This is not a local include */
#include "config.h"       /* This IS a local include */
</pre>
            </td>
          </tr>
        </table>

        <p><span class="emphasis EMPHASIS c2">Exception:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
/* This is not a local include, but requires a path element. */
#include &lt;sys/fileName.h&gt;
</pre>
            </td>
          </tr>
        </table>

        <p><span class="emphasis EMPHASIS c2">Note:</span> Please! do not add
        "-I." to the Makefile without a _very_ good reason. This duplicates
        the #include "file.h" behavior.</p>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S32" id="S32">4.6.7. Provide multiple
        inclusion protection</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>Prevents compiler and linker errors resulting from redefinition of
        items.</p>

        <p>Wrap each header file with the following syntax to prevent
        multiple inclusions of the file. Of course, replace PROJECT_H with
        your file name, with "." Changed to "_", and make it uppercase.</p>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
#ifndef PROJECT_H_INCLUDED
#define PROJECT_H_INCLUDED
 ...
#endif /* ndef PROJECT_H_INCLUDED */
</pre>
            </td>
          </tr>
        </table>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S33" id="S33">4.6.8. Use `extern "C"` when
        appropriate</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>If our headers are included from C++, they must declare our
        functions as `extern "C"`. This has no cost in C, but increases the
        potential re-usability of our code.</p>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
#ifdef __cplusplus
extern "C"
{
#endif /* def __cplusplus */

... function definitions here ...

#ifdef __cplusplus
}
#endif /* def __cplusplus */
</pre>
            </td>
          </tr>
        </table>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S34" id="S34">4.6.9. Where Possible, Use
        Forward Struct Declaration Instead of Includes</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>Useful in headers that include pointers to other struct's.
        Modifications to excess header files may cause needless compiles.</p>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
/*********************************************************************
 * We're avoiding an include statement here!
 *********************************************************************/
struct file_list;
extern file_list *xyz;
</pre>
            </td>
          </tr>
        </table>

        <p><span class="emphasis EMPHASIS c2">Note:</span> If you declare
        "file_list xyz;" (without the pointer), then including the proper
        header file is necessary. If you only want to prototype a pointer,
        however, the header file is unnecessary.</p>

        <p><span class="emphasis EMPHASIS c2">Status:</span> Use with
        discretion.</p>
      </div>
    </div>

    <div class="SECT2">
      <h2 class="SECT2"><a name="S35" id="S35">4.7. General Coding
      Practices</a></h2>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S36" id="S36">4.7.1. Turn on
        warnings</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation</span></p>

        <p>Compiler warnings are meant to help you find bugs. You should turn
        on as many as possible. With GCC, the switch is "-Wall". Try and fix
        as many warnings as possible.</p>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S37" id="S37">4.7.2. Provide a default
        case for all switch statements</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>What you think is guaranteed is never really guaranteed. The value
        that you don't think you need to check is the one that someday will
        be passed. So, to protect yourself from the unknown, always have a
        default step in a switch statement.</p>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
switch( hash_string( cmd ) )
{
   case hash_actions_file :
      ... code ...
      break;

   case hash_confdir :
      ... code ...
      break;

   default :
      log_error( ... );
      ... anomaly code goes here ...
      continue; / break; / exit( 1 ); / etc ...

} /* end switch( hash_string( cmd ) ) */
</pre>
            </td>
          </tr>
        </table>

        <p><span class="emphasis EMPHASIS c2">Note:</span> If you already
        have a default condition, you are obviously exempt from this point.
        Of note, most of the WIN32 code calls `DefWindowProc' after the
        switch statement. This API call *should* be included in a default
        statement.</p>

        <p><span class="emphasis EMPHASIS c2">Another Note:</span> This is
        not so much a readability issue as a robust programming issue. The
        "anomaly code goes here" may be no more than a print to the STDERR
        stream (as in load_config). Or it may really be an abort
        condition.</p>

        <p><span class="emphasis EMPHASIS c2">Status:</span> Programmer
        discretion is advised.</p>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S38" id="S38">4.7.3. Try to avoid falling
        through cases in a switch statement.</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>In general, you will want to have a 'break' statement within each
        'case' of a switch statement. This allows for the code to be more
        readable and understandable, and furthermore can prevent unwanted
        surprises if someone else later gets creative and moves the code
        around.</p>

        <p>The language allows you to plan the fall through from one case
        statement to another simply by omitting the break statement within
        the case statement. This feature does have benefits, but should only
        be used in rare cases. In general, use a break statement for each
        case statement.</p>

        <p>If you choose to allow fall through, you should comment both the
        fact of the fall through and reason why you felt it was
        necessary.</p>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S39" id="S39">4.7.4. Use 'long' or 'short'
        Instead of 'int'</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>On 32-bit platforms, int usually has the range of long. On 16-bit
        platforms, int has the range of short.</p>

        <p><span class="emphasis EMPHASIS c2">Status:</span> open-to-debate.
        In the case of most FSF projects (including X/GNU-Emacs), there are
        typedefs to int4, int8, int16, (or equivalence ... I forget the exact
        typedefs now). Should we add these to IJB now that we have a
        "configure" script?</p>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S40" id="S40">4.7.5. Don't mix size_t and
        other types</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>The type of size_t varies across platforms. Do not make
        assumptions about whether it is signed or unsigned, or about how long
        it is. Do not compare a size_t against another variable of a
        different type (or even against a constant) without casting one of
        the values.</p>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S41" id="S41">4.7.6. Declare each variable
        and struct on its own line.</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>It can be tempting to declare a series of variables all on one
        line. Don't.</p>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
long a = 0;
long b = 0;
long c = 0;
</pre>
            </td>
          </tr>
        </table>

        <p><span class="emphasis EMPHASIS c2">Instead of:</span></p>

        <p>long a, b, c;</p>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span> - there is
        more room for comments on the individual variables - easier to add
        new variables without messing up the original ones - when searching
        on a variable to find its type, there is less clutter to "visually"
        eliminate</p>

        <p><span class="emphasis EMPHASIS c2">Exceptions:</span> when you
        want to declare a bunch of loop variables or other trivial variables;
        feel free to declare them on one line. You should, although, provide
        a good comment on their functions.</p>

        <p><span class="emphasis EMPHASIS c2">Status:</span>
        developer-discretion.</p>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S42" id="S42">4.7.7. Use malloc/zalloc
        sparingly</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>Create a local struct (on the stack) if the variable will live and
        die within the context of one function call.</p>

        <p>Only "malloc" a struct (on the heap) if the variable's life will
        extend beyond the context of one function call.</p>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
If a function creates a struct and stores a pointer to it in a
list, then it should definitely be allocated via `malloc'.
</pre>
            </td>
          </tr>
        </table>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S43" id="S43">4.7.8. The Programmer Who
        Uses 'malloc' is Responsible for Ensuring 'free'</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>If you have to "malloc" an instance, you are responsible for
        insuring that the instance is `free'd, even if the deallocation event
        falls within some other programmer's code. You are also responsible
        for ensuring that deletion is timely (i.e. not too soon, not too
        late). This is known as "low-coupling" and is a "good thing (tm)".
        You may need to offer a free/unload/destructor type function to
        accommodate this.</p>

        <p><span class="emphasis EMPHASIS c2">Example:</span></p>

        <table class="c3" border="0" width="100%">
          <tr>
            <td>
              <pre class="PROGRAMLISTING">
int load_re_filterfile( struct client_state *csp ) { ... }
static void unload_re_filterfile( void *f ) { ... }
</pre>
            </td>
          </tr>
        </table>

        <p><span class="emphasis EMPHASIS c2">Exceptions:</span></p>

        <p>The developer cannot be expected to provide `free'ing functions
        for C run-time library functions ... such as `strdup'.</p>

        <p><span class="emphasis EMPHASIS c2">Status:</span>
        developer-discretion. The "main" use of this standard is for
        allocating and freeing data structures (complex or nested).</p>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S44" id="S44">4.7.9. Add loaders to the
        `file_list' structure and in order</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>I have ordered all of the "blocker" file code to be in alpha
        order. It is easier to add/read new blockers when you expect a
        certain order.</p>

        <p><span class="emphasis EMPHASIS c2">Note:</span> It may appear that
        the alpha order is broken in places by POPUP tests coming before PCRS
        tests. But since POPUPs can also be referred to as KILLPOPUPs, it is
        clear that it should come first.</p>
      </div>

      <div class="SECT3">
        <h3 class="SECT3"><a name="S45" id="S45">4.7.10. "Uncertain" new code
        and/or changes to existing code, use FIXME or XXX</a></h3>

        <p><span class="emphasis EMPHASIS c2">Explanation:</span></p>

        <p>If you have enough confidence in new code or confidence in your
        changes, but are not *quite* sure of the repercussions, add this:</p>

        <p>/* FIXME: this code has a logic error on platform XYZ, *
        attempting to fix */ #ifdef PLATFORM ...changed code here...
        #endif</p>

        <p>or:</p>

        <p>/* FIXME: I think the original author really meant this... */
        ...changed code here...</p>

        <p>or:</p>

        <p>/* FIXME: new code that *may* break something else... */ ...new
        code here...</p>

        <p><span class="emphasis EMPHASIS c2">Note:</span> If you make it
        clear that this may or may not be a "good thing (tm)", it will be
        easier to identify and include in the project (or conversely exclude
        from the project).</p>
      </div>
    </div>

    <div class="SECT2">
      <h2 class="SECT2"><a name="S46" id="S46">4.8. Addendum: Template for
      files and function comment blocks:</a></h2>

      <p><span class="emphasis EMPHASIS c2">Example for file
      comments:</span></p>

      <table class="c3" border="0" width="100%">
        <tr>
          <td>
            <pre class="PROGRAMLISTING">
const char FILENAME_rcs[] = "$Id: coding.html,v 1.58 2011/12/26 17:06:24 fabiankeil Exp $";
/*********************************************************************
 *
 * File        :  $Source: /cvsroot/ijbswa/current/doc/webserver/developer-manual/coding.html,v $
 *
 * Purpose     :  (Fill me in with a good description!)
 *
 * Copyright   :  Written by and Copyright (C) 2001-2009
 *                the Privoxy team. http://www.privoxy.org/
 *
 *                This program is free software; you can redistribute it
 *                and/or modify it under the terms of the GNU General
 *                Public License as published by the Free Software
 *                Foundation; either version 2 of the License, or (at
 *                your option) any later version.
 *
 *                This program is distributed in the hope that it will
 *                be useful, but WITHOUT ANY WARRANTY; without even the
 *                implied warranty of MERCHANTABILITY or FITNESS FOR A
 *                PARTICULAR PURPOSE.  See the GNU General Public
 *                License for more details.
 *
 *                The GNU General Public License should be included with
 *                this file.  If not, you can view it at
 *                http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 *                or write to the Free Software Foundation, Inc.,
 *                51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 ,
 *                USA
 *
 *********************************************************************/


#include "config.h"

   ...necessary include files for us to do our work...

const char FILENAME_h_rcs[] = FILENAME_H_VERSION;
</pre>
          </td>
        </tr>
      </table>

      <p><span class="emphasis EMPHASIS c2">Note:</span> This declares the
      rcs variables that should be added to the "show-proxy-args" page. If
      this is a brand new creation by you, you are free to change the
      "Copyright" section to represent the rights you wish to maintain.</p>

      <p><span class="emphasis EMPHASIS c2">Note:</span> The formfeed
      character that is present right after the comment flower box is handy
      for (X|GNU)Emacs users to skip the verbiage and get to the heart of the
      code (via `forward-page' and `backward-page'). Please include it if you
      can.</p>

      <p><span class="emphasis EMPHASIS c2">Example for file header
      comments:</span></p>

      <table class="c3" border="0" width="100%">
        <tr>
          <td>
            <pre class="PROGRAMLISTING">
#ifndef _FILENAME_H
#define _FILENAME_H
#define FILENAME_H_VERSION "$Id: coding.html,v 1.58 2011/12/26 17:06:24 fabiankeil Exp $"
/*********************************************************************
 *
 * File        :  $Source: /cvsroot/ijbswa/current/doc/webserver/developer-manual/coding.html,v $
 *
 * Purpose     :  (Fill me in with a good description!)
 *
 * Copyright   :  Written by and Copyright (C) 2001-2009
 *                the Privoxy team. http://www.privoxy.org/
 *
 *                This program is free software; you can redistribute it
 *                and/or modify it under the terms of the GNU General
 *                Public License as published by the Free Software
 *                Foundation; either version 2 of the License, or (at
 *                your option) any later version.
 *
 *                This program is distributed in the hope that it will
 *                be useful, but WITHOUT ANY WARRANTY; without even the
 *                implied warranty of MERCHANTABILITY or FITNESS FOR A
 *                PARTICULAR PURPOSE.  See the GNU General Public
 *                License for more details.
 *
 *                The GNU General Public License should be included with
 *                this file.  If not, you can view it at
 *                http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 *                or write to the Free Software Foundation, Inc.,
 *                51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 ,
 *                USA
 *
 *********************************************************************/


#include "project.h"

#ifdef __cplusplus
extern "C" {
#endif

   ... function headers here ...


/* Revision control strings from this header and associated .c file */
extern const char FILENAME_rcs[];
extern const char FILENAME_h_rcs[];


#ifdef __cplusplus
} /* extern "C" */
#endif

#endif /* ndef _FILENAME_H */

/*
  Local Variables:
  tab-width: 3
  end:
*/
</pre>
          </td>
        </tr>
      </table>

      <p><span class="emphasis EMPHASIS c2">Example for function
      comments:</span></p>

      <table class="c3" border="0" width="100%">
        <tr>
          <td>
            <pre class="PROGRAMLISTING">
/*********************************************************************
 *
 * Function    :  FUNCTION_NAME
 *
 * Description :  (Fill me in with a good description!)
 *
 * parameters  :
 *          1  :  param1 = pointer to an important thing
 *          2  :  x      = pointer to something else
 *
 * Returns     :  0 =&gt; Ok, everything else is an error.
 *
 *********************************************************************/
int FUNCTION_NAME( void *param1, const char *x )
{
   ...
   return( 0 );

}
</pre>
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      <p><span class="emphasis EMPHASIS c2">Note:</span> If we all follow
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